i have been collecting glass bottles from my local pub and still have not got all the ones i need, so what i will have to get is some 500ml spring water from tescos at £1.88 for 8 and ill need 32 so its £7.52 or i can get 2ltr spring water bottels at 12p each, so i need 13 which is £1.56. now if i use the 2ltr bottles can i open it and not use all the brew will it keep for a few days after opening or will it go off.